Technical Abstract:
Metabolic syndrome, a leading cause of diabetes and cardiovascular diseases, is characterized by insulin resistance, atherogenic dyslipidemia and increased oxidative stress. Tea polyphenols, as both insulin potentiating factors and antioxidants, might act in preventing the metabolic syndrome. Therefore, the aim of this study was to determine the beneficial effects of green tea consumption on insulin sensitivity and oxidative stress using an animal model of the metabolic syndrome. Wistar rats, 10 per group, received a high fructose diet for six weeks to induce the metabolic syndrome or the same high fructose diet plus either 1 or 2 g of green tea solid extracts/kg diet. In rats receiving tea solids, there were significant decreases in plasma lipid peroxidation, sulfhydryl group oxidation and DNA oxidative damage. The antioxidant metalloenzymes, superoxide dismutase, glutathione peroxidase and catalase, were significantly lower. There were also significant improvements in glucose, insulin, cholesterol and triglycerides in animals receiving the diets containing the tea solids. Beneficial effects tended to be greater in animals consuming the lower level of tea solids. Changes in adiponectin, leptin and corticosterone were not significant. In summary, our data demonstrate that green tea solids act in preventing the metabolic syndrome as insulin sensitizers and through their antioxidant functions. This study suggests that green tea may be of benefit for people at high risk of the metabolic syndrome and diabetes.